For a limited time, you can earn extra miles and up to $50 of statement credits when you take Lyft rides.

American Express and Delta offer a few different flavors of their co-branded credit cards, each with a slightly different set of benefits. While some, like the Gold Delta SkyMiles card, offer benefits like free checked bags and priority boarding, these co-branded cards have annual fees of at least $95. In the case of the Gold card, it's waived for the first year.

However, Delta and Amex also offer a no-annual-fee card for people who want to earn Delta miles from their spending, but don't want to pay the annual fee (or don't need the free checked bag).

The Blue Delta SkyMiles card from Amex is basically a stripped down — and free — version of the other co-branded cards. It offer 2x Delta SkyMiles earned on every dollar spent with Delta and at US restaurants, and 1x mile per dollar on everything else. It also gets you a 20% discount — in the form of a statement credit — on Delta in-flight purchases like food or drinks.

For a limited time, there's another bonus category: For your first six months of card membership, you'll earn 2x miles per dollar spent and up to $50 in statement credits on purchases with ride-sharing app Lyft. Delta and Lyft already have a partnership in place — you can connect your accounts and earn Delta SkyMiles on every Lyft trip — so this new benefit makes sense. This is only available if you apply for the card before October 18, so it looks like this won't be a permanent fixture.

The Blue Delta card also offers 10,000 SkyMiles when you spend $500 on any purchases in the first three months. While that isn't the world's biggest offer — for instance, the Gold version offers 30,000 miles after spending $3,000 in the first three months, and has been higher in the past — it's solid for a no-fee card. It can be a nice addition to your current stock of Delta miles.

While more frequent Delta flyers who can make good use of the priority boarding and free checked bag may want to consider the Gold Delta card, the Blue is a good option for anyone who doesn't want to pay an annual fee, but still wants to earn Delta miles and get in-flight discounts.

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